Clinical and laboratory studies are conducted to determine etiology (infection, immunity and/or genetics) for chronic diseases of the peripheral and central nervous system). Current studies include amyotrophic lateral sclerosis, (ALS), polymyositis/dermatomyositis, demyelinating polyneuropathies, progressive multifocal leukoencephalopathy, and myasthenia gravis. Combined clinical data, genetic information, HLA and MLC typing and studies of virus serology and virus isolation are performed. The nature of oligoclonal bands found in the CSF of patients with chronic neurological diseases is under investigation. A neuromuscular disease that occurs in patients who have had poliomyelitis at an early age has been clinically defined; the possibility that this might be due to a late polio virus infection or an abnormal immunoregulation and an immune reaction to neuronal cells is under investigation. IgM monoclonal band has been identified in the spinal fluid of patients with paraproteinemic polyneuropathies and an abnormal blood-CSF was found. The pathogenetic mechanisms of patients with a chronic, sensory, "ataxic" neuropathy were examined and the role of proprioceptive afferent inputs for their postural maintenance was investigated. The metabolic activity of the cortex in ALS patients is being studied using the PET scan and 18F 2-deoxy-D-glucose; hypometabolism was demonstrated not only in the motor but also in the paramotor and sensory cortex, suggesting that ALS is a rather generalized process affecting many cortical regions. The effect of aging on the neuromuscular systems is being investigated electrophysiologically and morphologically, in the muscle and nerve biopsies of normal elderly patients and patients with Alzheimer's disease. Muscle biopsies from patients with nephropathic cystinosis and renal Fanconi syndrome were studied morphologically and biochemically. Signs of a metabolic lipid storage myopathy due to carnitine deficiency were found; this prompted us to start a therapeutic study with carnitine replacement.